1 files changed, 115 insertions, 0 deletions
diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
new file mode 100644
index 000000000..f9c00110a
--- /dev/null
+++ b/arch/x86/include/asm/futex.h
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_FUTEX_H
+#define _ASM_X86_FUTEX_H
+
+#ifdef __KERNEL__
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+
+#include <asm/asm.h>
+#include <asm/errno.h>
+#include <asm/processor.h>
+#include <asm/smap.h>
+
+#define unsafe_atomic_op1(insn, oval, uaddr, oparg, label)	\
+do {								\
+	int oldval = 0, ret;					\
+	asm volatile("1:\t" insn "\n"				\
+		     "2:\n"					\
+		     "\t.section .fixup,\"ax\"\n"		\
+		     "3:\tmov\t%3, %1\n"			\
+		     "\tjmp\t2b\n"				\
+		     "\t.previous\n"				\
+		     _ASM_EXTABLE_UA(1b, 3b)			\
+		     : "=r" (oldval), "=r" (ret), "+m" (*uaddr)	\
+		     : "i" (-EFAULT), "0" (oparg), "1" (0));	\
+	if (ret)						\
+		goto label;					\
+	*oval = oldval;						\
+} while(0)
+
+
+#define unsafe_atomic_op2(insn, oval, uaddr, oparg, label)	\
+do {								\
+	int oldval = 0, ret, tem;				\
+	asm volatile("1:\tmovl	%2, %0\n"			\
+		     "2:\tmovl\t%0, %3\n"			\
+		     "\t" insn "\n"				\
+		     "3:\t" LOCK_PREFIX "cmpxchgl %3, %2\n"	\
+		     "\tjnz\t2b\n"				\
+		     "4:\n"					\
+		     "\t.section .fixup,\"ax\"\n"		\
+		     "5:\tmov\t%5, %1\n"			\
+		     "\tjmp\t4b\n"				\
+		     "\t.previous\n"				\
+		     _ASM_EXTABLE_UA(1b, 5b)			\
+		     _ASM_EXTABLE_UA(3b, 5b)			\
+		     : "=&a" (oldval), "=&r" (ret),		\
+		       "+m" (*uaddr), "=&r" (tem)		\
+		     : "r" (oparg), "i" (-EFAULT), "1" (0));	\
+	if (ret)						\
+		goto label;					\
+	*oval = oldval;						\
+} while(0)
+
+static __always_inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+		u32 __user *uaddr)
+{
+	if (!user_access_begin(uaddr, sizeof(u32)))
+		return -EFAULT;
+
+	switch (op) {
+	case FUTEX_OP_SET:
+		unsafe_atomic_op1("xchgl %0, %2", oval, uaddr, oparg, Efault);
+		break;
+	case FUTEX_OP_ADD:
+		unsafe_atomic_op1(LOCK_PREFIX "xaddl %0, %2", oval,
+				   uaddr, oparg, Efault);
+		break;
+	case FUTEX_OP_OR:
+		unsafe_atomic_op2("orl %4, %3", oval, uaddr, oparg, Efault);
+		break;
+	case FUTEX_OP_ANDN:
+		unsafe_atomic_op2("andl %4, %3", oval, uaddr, ~oparg, Efault);
+		break;
+	case FUTEX_OP_XOR:
+		unsafe_atomic_op2("xorl %4, %3", oval, uaddr, oparg, Efault);
+		break;
+	default:
+		user_access_end();
+		return -ENOSYS;
+	}
+	user_access_end();
+	return 0;
+Efault:
+	user_access_end();
+	return -EFAULT;
+}
+
+static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+						u32 oldval, u32 newval)
+{
+	int ret = 0;
+
+	if (!user_access_begin(uaddr, sizeof(u32)))
+		return -EFAULT;
+	asm volatile("\n"
+		"1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n"
+		"2:\n"
+		"\t.section .fixup, \"ax\"\n"
+		"3:\tmov     %3, %0\n"
+		"\tjmp     2b\n"
+		"\t.previous\n"
+		_ASM_EXTABLE_UA(1b, 3b)
+		: "+r" (ret), "=a" (oldval), "+m" (*uaddr)
+		: "i" (-EFAULT), "r" (newval), "1" (oldval)
+		: "memory"
+	);
+	user_access_end();
+	*uval = oldval;
+	return ret;
+}
+
+#endif
+#endif /* _ASM_X86_FUTEX_H */